1. Field of the Invention
This invention relates to the field of catheters and in particular to coronary dilation catheter assemblies utilizing a perfusion balloon at one end thereof.
2. Background Art
A blood vessel of a circulatory system can often become narrow to the point where the flow of blood is limited or severely restricted. This narrowing of the blood vessel region is called a "stenosis" and is caused by the growth or development of a mass or lesion on the inner walls of the blood vesse. The stenosis must be removed, compressed, or bypassed to restore maximum blood flow capability to the blood vessel. Presently, the methods for treating stenosis of a blood vessel comprise either a surgical procedure or angioplasty.
The method known as angioplasty involves the insertion of a balloon catheter into a blood vessel at the stenotic region. The balloon is then inflated to compress the lesion material comprising the stenosis back against the walls of the blood vessel and ideally, permanently compressing the lesion material to increase the diameter of the blood vessel and hence blood flow rate of the blood vessel.
Prior art angioplasty catheters comprise a guide wire designed as either part of an angioplasty catheter or to fit inside one which is inserted through a guiding catheter into the circulatory system at some location and advanced through the blood vessel to a point past the stenosis. A balloon catheter comprising a balloon fastened around the exterior of a hollow catheter tube is inserted about the wire and slid over the guide wire until it is at the point of the stenosis.
Once in place, the balloon is inflated with a suitable fluid to dilate the lesion causing the stenosis. The balloon is then deflated and the stenotic region is observed to see if blood flow is restored. This may involved completely removing the catheter assembly and measuring the rate of blood flow through the blood vessel. If the stenosis is not compressed and springs back into place, closing the vessel, or if the blood vessel completely collapses, the patient may need to undergo surgery if the blood vessel cannot be maintained open by further dilatations. This must be done as soon as possible because a blood vessel cannot be blocked for more than a short period of time without damaging the tissue that it supplies. Therefore, while the catheter procedure can often prevent the need for surgery, it is still necessary to have the surgeons and operating room on standby during the procedure, tus incurring the expense of preparing completely for surgery during the procedure.
One disadvantage of such prior art balloon catheters is the complete occlusion of the vessel during the angioplasty process. Typically, the balloon can only remain inflated for a few secons before it must be deflated to permit blood flow to continue. Further, the catheter often must be completely removed from the blood vessel to determine if the procedure was successful.
Therefore, it is desirable to provide an angioplasty catheter in which a blood flow path is provided past the stenotic region of a blood vessel receiving the angioplasty treatment. It is also desirable to provide a catheter assembly which can be left in place while the effectiveness of treatment is determined. One prior art attempt to provide such a catheter is described in U.S. Pat. No. 4,581,017 to Sahota. There, small orifices are provided in the proximal end of the balloon catheter adjacent to the balloon and at the distal end of the catheter adjacent to the balloon. These orifices provide a flow path for blood during the angioplasty process. The orifices are designed to provide blood flow while the balloon remains inflated and if, after the balloon is deflated, the blood vessel collapses. However, the device of Sahota still results in insufficient cross sectional flow area in the blood vessel.
It is also desired to provide a balloon catheter which can be used for valvuloplasty procedures. At the present tme, when a valvuloplasty balloon dilatation cathether is inflated across a stenotic heart valve, the heart continues to pump against a completely obstructed valve apparatus, placing severe stress on the heart muscle.
Therefore, it is an object of the present invention to provide a balloon catheter which permits blood flow while the balloon is inflated.
It is a further object of the present invention to provide a balloon catheter which can be kept in place and inflated while the patient is prepared for surgery.
It is still another object of the present invention to provide a balloon catheter which can be utilized for valvuloplasty.